The present disclosure relates in general to nuclear medicine and generators for the production of radiopharmaceuticals for medical use. In particular, present disclosure relates to a generator column that resists high heat such as depyrogenation and sterilization. This allows some steps of the preparation of the column to be performed in a non-sterile environment. This also allows the generator column to be reusable. The present disclosure further describes methods for the preparation of a generator where a parent radioisotope is charged on the column matrix before or after the matrix is loaded in the column.